Method of manufacturing coated cutting tool and coated cutting tool made from

ABSTRACT

A method of preparing a coated cutting tool is provided involving formation of a hard coating layer including an aluminum oxide layer to an average layer thickness of 3-20 microns on the surface of a cutting tool substrate using chemical vapor deposition and/or physical vapor deposition, to give a coated cutting tool excellent in chipping resistance, where the aluminum oxide layer is formed from an inert gas type reaction gas containing aluminum chloride and nitrogen oxides, and optionally titanium tetrachloride, nitrogen and hydrogen, in an inert carrier gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a coatedcutting tool to provide a hard coating layer comprising an aluminumoxide overlayer and having a uniform layer thickness even at highthicknesses, as well as excellent adhesion to other layers of thecutting tool, wherein the tool exhibits excellent chipping resistancefor extended periods of time in both continuous and intermittentcutting.

2. Discussion of the Background

Hard-material-coated sintered carbide cutting tools made of a cementedtungsten carbide-based substrate (hereinafter, referred to as a cementedcarbide substrate), the surface of which is coated with a hard coatinglayer comprising an Al₂ O₃ layer are known. For example, hard coatinglayers composed of an Al₂ O₃ layer and one, two or more of a titaniumcarbide (TiC) layer, a titanium nitride (TiN) layer, a titaniumcarbonitride (TiCN) layer, a titanium oxide (TiO₂) layer, a titaniumoxycarbide (TiCO) layer, a titanium oxynitride (TiNO) layer, and atitanium oxycarbonitride (TiCNO) layer deposited using chemical vapordeposition and/or physical vapor deposition to an average layerthickness of 3-20 microns are known.

Further, it is also known to form the Al₂ O₃ layer of the coatedcemented carbide cutting tool using a reaction gas having the followingcomposition in vol % (hereinafter referred to merely as %, unlessotherwise specified): Aluminum trichloride (AlCl₃): 1-20%; Carbondioxide (CO₂): 1-20% (optionally, carbon monoxide (CO) or hydrogenchloride (HCl): 1-30%) and Hydrogen: remainder, at a reactiontemperature of 950°-1100° C. and an atmospheric pressure of 20-200 torrof hydrogen.

Recently, there has been a strong tendency towards providing automaticcutting operations and labor cost savings in factories. Accordingly itis required to prolong the usable life of coated tools. As one means forcoping with this requirement, the thickness of the Al₂ O₃ layer has beenincreased to provide improved oxidation resistance, thermal stabilityand high hardness among the hard coating layers constituting the tool.However when the Al₂ O₃ layer is made thicker, relative to other partsof the hard coating layer, the layer thickness thereof is made locallyuneven by the use of the above-noted conventional Al₂ O₃ layer formingmethods. As a result, not only is the layer thickness highly variableamong the flank face, the rake face, and the cutting edge of the insertbut also the adhesion (interlayer adhesion) of the Al₂ O₃ layer withother constituting layers is lowered. Because of this, the cutting edgetends to chip when the tool is used in intermittent cutting of metals,such as steel or cast iron, and the usable life of the tool is spent ina relatively short period of time.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a methodfor the preparation of an Al₂ O₃ layer in a coating layer of a coatedcemented carbide cutting tool that reduces chipping and provides longertool lifetime in both continuous and intermittent cutting of metals.

A further object of the present invention is to provide a method for thepreparation of an Al₂ O₃ layer in a coating layer of a coated cementedcarbide cutting tool that provides improved layer thickness consistency.

A further object of the present invention is to provide a method for thepreparation of an Al₂ O₃ layer in a coating layer of a coated cementedcarbide cutting tool that provides improved interlayer adhesion.

These and other objects of the present invention have been satisfied bythe discovery of a method for preparing a coated cutting toolcomprising:

coating a surface of a substrate with a hard coating layer comprising analuminum oxide layer, using chemical vapor deposition, physical vapordeposition or both, wherein the aluminum oxide layer is formed from areaction gas comprising aluminum trichloride and nitrogen oxides in aninert gas as carrier gas.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a method for preparing a coated cuttingtool comprising:

coating a surface of a substrate with a hard coating layer comprising analuminum oxide layer, using chemical vapor deposition, physical vapordeposition or both, wherein the aluminum oxide layer is formed from areaction gas comprising aluminum trichloride and nitrogen oxides in aninert gas as carrier gas.

The present inventors have made the following observations:

(A) In an Al₂ O₃ layer formed using a conventional hydrogen atmosphere,CO₂ and hydrogen (H₂) as components constituting the reaction gas, thecomponents react with each other according to the following reactionformula (1).

    CO.sub.2 +H.sub.2 →CO+H.sub.2 O                     (1)

The resultant H₂ O reacts with AlCl₃ according to the following reactionformula (2) so that Al₂ O₃ is created by the hydrolysis of AlCl₃.

    AlCl.sub.3 +H.sub.2 O→Al.sub.2 O.sub.3 +HCl         (2)

In this case, since the reaction based on the formula (2) has asignificantly higher reaction rate compared with the reaction based onthe formula (1), H₂ O created by the formula (1) is immediately reactedwith AlCl₃ existing in the reaction atmosphere. Therefore, almost all ofthe Al₂ O₃ is created in the gas phase and consequently the Al₂ O₃ layeris formed by the deposition of Al₂ O₃ nuclei onto the surface ofsubstrate. Consequently, it is difficult to form Al₂ O₃ layers having auniform layer thickness on the flank face, the rake face of a cuttingportion and the cutting edge where the flank face intersects the rakeface even if, for example, a cutting insert is placed in the flow of thereaction gas in any state. This difficulty is also increased since theAl₂ O₃ layers are affected by the flow of the reaction gas and the shapeof the substrate. Thus there is great dispersion in the layer thickness.

(B) Based on observation (A) above, the present inventors concluded thatwhen a layer is made by creating Al₂ O₃ nuclei adjacent and as close aspossible to the surface, the layer thickness thereof can be madeuniform. Thus, the inventors have developed an inert gas type reactiongas which permits such layer formation. The present method uses thisreaction gas having the following composition by volume:

AlCl₃ : 0.5-10%

Nitrogen oxides (hereinafter, shown by NO_(x)): 1-30%

Inert gas as the carrier gas: remainder

When the inert gas type reaction gas mentioned above is used, NO_(x) isdissolved at the surface of substrate according to the followingreaction formula (a) and O created by the reaction according to theformula (a) is adsorbed to that surface, thus, the above O reacts withAlCl₃ at that surface according to the following reaction formula (b).

    NO.sub.x →N.sub.2 +O                                (a)

    AlCl.sub.3 +O→Al.sub.2 O.sub.3 +Cl.sub.2            (b)

Therefore, the layer is formed in a state where the Al₂ O₃ nuclei aremainly formed at the surface of the substrate, instead of in the gasphase, and the deposited layer is not significantly affected by the flowof the reaction gas and the shape of the substrate. As a result, theresultant deposited layer has a very small amount of local dispersioneven if it is formed into a thick layer and further the adhesion of thelayer to the substrate is enhanced. In addition, since the depositedlayer is mainly composed of Al₂ O₃, that is, an aluminum oxide layer inwhich the content of the components constituting the reaction gas exceptAl and oxygen is 15% or less and preferably 10% or less, the depositedlayer has oxidation resistance, thermal stability and high hardnesssimilar to the characteristics provided with Al₂ O₃.

(C) TiCl₄, ZrCl₄ and HfCl₄ gases additionally mixed with the reactiongas act as a catalyst for the reaction NO_(x) →N₂ +O (a)

Note, the aluminum oxide layer of the present invention is describedherein as a crystalline/non-crystalline aluminum oxide compound layer inwhich the content of the components other than Al and O constituting thereaction gas is 15% or less.

The present invention relates to a method for preparing a coated tool byforming a hard coating layer comprising an aluminum oxide layer,preferably a hard coating layer having an average layer thickness of3-20 microns and comprising the aluminum oxide layer and one, two ormore of a TiC layer, a TiN layer, a TiCN layer, a TiO₂ layer, a TiCOlayer, a TiNO layer, and a TiCNO layer. The aluminum oxide layer isformed on the surface of a substrate using chemical vapor depositionand/or physical vapor deposition from a reaction gas comprising AlCl₃and NO_(x) with an inert gas as carrier. The present method preferablyforms the aluminum oxide layer constituting the hard coating layer as arelatively thick layer (compared to conventional Al₂ O₃ layers) using aninert gas-type reaction gas having the following composition:

AlCl₃ : 0.5-10%

NO_(x) : 1-30%

TiCl₄ : 0-15%

N₂ : 0-15%

H₂ : 0-20%

with the proviso that when TiCl₄ is present in the reaction gas, thevolume ratio of Al₂ O₃ :TiCl₄ is from 5 to 100; with the remainder ofthe reaction gas being an inert gas.

The present method provides a coated cutting tool in which the layerthickness of the Al₂ O₃ layer is more uniform and has enhanced adhesionto provide excellent chipping resistance.

When the amount of AlCl₃ in the reaction gas is less than 0.5%, theformation of the aluminum oxide layer is slowed to a practicallyunacceptable level due to insufficient amounts of an Al source. When theamount exceeds 10%, since the Al source is excessively supplied, thecrystallinity of the aluminum oxide layer (deposited layer) is lowered.Thus the amount is preferably set to 0.5-10%, more preferably to 2-7%.

When the amount of NO_(x) in the reaction is less than 1%, thecrystallinity of the deposited layer is lowered due to an insufficientsupply of O relative to the amount of Al. When the amount of NO_(x)exceeds 30%, there is too much dissolved O relative to the Al source,causing localized fluctuations in layer thickness due to the reaction:

    AlCl.sub.3 +O→Al.sub.2 O.sub.3 +Cl.sub.2

Thus, the uniformity of the layer thickness is lowered. Accordingly, theamount is preferably set to 1-30%, more preferably to 5-20%.

TiCl₄ is an optional component of the reaction gas of the present methodwhich can be used to accelerate the reaction of the formula (a) NO_(x)→N₂ +O. When the amount of TiCl₄ is less than 0.01%, the progress of thereaction of the above formula (a) can be insufficient, thus causing thesupply of O for the preparation of Al₂ O₃ to be insufficient. Under suchconditions, the Al₂ O₃ cannot be formed at a practical speed and thethickness uniformity of the layer is damaged. When the amount of TiCl₄exceeds 1%, a large amount of Ti exists in the reaction atmospherecausing the crystallinity of the deposited layer to be lowered. Thus,the TiCl₄ amount is preferably set to 0.01-1%, more preferably to0.1-0.5%.

While H₂ is an optional component of the reaction gas of the presentmethod which activates the reaction atmosphere, when the amount of H₂ isless than 0.5%, the reaction atmosphere can be difficult to activate tothe desired high level. When the amount of H₂ exceeds 20%, the layerthickness of the deposited layer is made uneven. Thus, the amount of H₂is preferably set to 0.5-20%, more preferably to 1-10%.

N₂ has a stabilizing effect on the reaction of formula (a) above. Thisstabilization presumably is caused by suppressing the mutual bonding ofcreated O. When the amount of N₂ is less than 1%, this stabilizationeffect cannot be sufficiently maintained, while when the amount of N₂exceeds 15%, there is a tendency that the speed of formation of thedeposited layer is lowered. Thus, the amount of N₂ in the reaction ispreferably set to 1-15%, more preferably to 4-10%.

When TiCl₄ is used as an optional component of the reaction gas, theratios by volume of AlCl₃ :TiCl₄ should be maintained to balance thecrystallinity of the formed layer and the layer forming speed. When thevolume ratio of AlCl₃ :TiCl₄ is less than 5, the resulting ratio of Tisource to Al source in the reaction atmosphere is excessively increased,thus lowering the crystallinity of the deposited layer and the requiredlayer characteristics cannot be provided in the aluminum oxide layer.When the ratio of AlCl₃ :TiCl₄ exceeds 100, the ratio of Ti:Al in thereaction atmosphere is excessively decreased. This causes the NO_(x)dissolving action carried out by Ti on the surface of the substrate tobe greatly lowered, particularly at a reaction temperature equal to orless than 1000° C. Further, the O source for production of Al₂ O₃ isthen insufficient and the layer forming speed is lowered. Thus, whenTiCl₄ is present in the reaction gas, the ratio of AlCl₃ :TiCl₄ is setto 5-100, preferably to 10-100 and more preferably to 10-50.

The reaction temperature for the present process is preferably850°-1150° C., more preferably 900°-1100° C. and the atmosphericpressure is preferably 20-200 torr, more preferably 40-100 torr. Whenthe reaction temperature is less than 850° C., the crystallinity of thedeposited layer tends to be lowered, whereas when the temperatureexceeds 1150° C., the aluminum oxide layer is coarsened and wearresistance is lowered. In addition, when the atmospheric pressure isless than 20 torr, the reaction is slowed and the layer is not formed ata sufficiently desirable speed, whereas when the pressure exceeds 200torr, the surface of the aluminum oxide layer is made irregular, causingthe coating layer thickness to be uneven.

The average layer thickness of the hard coating layer is preferably setto 3-20 microns. When the layer thickness is less than 3 microns, thedesired excellent wear resistance cannot be provided, whereas when thelayer thickness exceeds 20 microns, the cutting edge is likely to breakand chip.

The present method can be applied to other substrates besides cementedcarbides, including, but not limited to Al₂ O₃, AlN, Si₃ N₄ or SiC basedsubstrates and their combination type ceramics and TiC, TiN, TiCN basedcermets which are stable under the conditions of the present method.

Further, the method can be used to provide a wide variety of coatedcutting tools required for longer tool life, including but not limitedto, cutting inserts, reamers, and end mills.

EXAMPLES

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

Example 1

The following powder materials were prepared: medium grain WC powderhaving an average grain size of 2.8 microns, rough grain WC powderhaving an average grain size of 4.9 microns, (Ti, W) C (TiC/WC in a30/70 weight ratio) powder having an average grain size of 1.5 microns,(Ti, W) CN (TiC/TiN/WC in a 24/20/56 weight ratio) powder having anaverage grain size of 1.2 microns, (Ta, Nb) C (TaC/NbC in a 90/10 weightratio) powder having an average grain size of 1.2 microns, and Co powderhaving an average grain size of 1.1 microns. These powder materials wereblended to have the blended compositions shown in Table 1 and wet mixedin a ball mill for 72 hours and dried. Then, they were molded to greencompacts having the shapes regulated by ISO/CNMG120408 (for cementedcarbide substrates A-D) and ISO/SEEN42AFTN1 (for cemented carbidesubstrate E) by a press. The resultant green compacts were made into thecemented carbide substrates A-E by being subjected to vacuum sinteringunder the conditions also shown in Table 1, respectively.

The cemented carbide substrate B was held in an atmosphere of CH₄ gas ata gas pressure of 100 torr at 1,400° C. for one hour and then subjectedto carburization while being gradually cooled. After the processing, aCo-enriched-zone having a maximum Co content of 15.9 wt% and a depth of42 microns was formed on the surface of the substrate by removing carbonand Co attached to the surface of the cemented carbide substrate by acidand barrel grinding.

Each of the cemented carbide substrates A and D had a Co-enriched-zonehaving a maximum Co content of 9.1 wt% and a depth of 23 microns,whereas the remaining cemented carbide substrates C and E had noCo-enriched-zone formed thereon and had a uniform structure as a whole.Table 1 shows the internal hardness of cemented carbide substrates A-E.(Rockwell hardness: A scale). The edges of these cemented carbidesubstrates A-E were subjected to honing.

Next, reactions 1-15 of the present invention and conventional reactions1-10 were performed and coated cemented carbide tools (hereinafter,coated cemented carbide tools corresponding to the respective methodsare referred to as present coated cutting tools 1-15 and conventionalcoated cutting tools 1-10) were manufactured by forming hard coatinglayers having the compositions and target layer thicknesses (at theflank face) shown in Tables 4 and 5 using conventional chemical vapordeposition, under the conditions shown in Table 2 (1 -TiCN in Table 2has a longitudinally-grown crystal structure as disclosed in JapaneseUnexamined Patent Publication No. 6-8010 and p-TiCN in Table 2 has anordinary grain-shaped crystal structure) and Table 3 (Al₂ O₃ (a) -(n) inTable 3 show aluminum oxide layers and Al₂ O₃ (o) shows an Al₂ O₃ layer,which are also applicable to Tables 4 and 5).

As to each of the aluminum oxide layers and the Al₂ O₃ layers (referredto collectively as Al₂ O₃ layers in Tables 6 and 7) constituting thehard coating layers of the various resultant coated cemented carbidetools, the maximum layer thickness of the cutting edge where a flankface intersected a rake face was measured and further the layerthicknesses on the flank face and the rake face which were located 1 mminward from the cutting edge were measured. Tables 6 and 7 show theresults of the measurements.

The layer thicknesses of the layers constituting the hard coating layer,other than the aluminum oxide layer and the Al₂ O₃ layer, had almost nolocal dispersion and exhibited almost the same values as the targetlayer thicknesses.

The elemental compositions of the aluminum oxide layer of thehard-material-coated cutting tools of the present invention and of theAl₂ O₃ layer of the conventional hard-material-coated cutting tools wereanalyzed using an EPMA. For those tools having an outermost layercomposed of TiN, the analysis was carried out after the removal of theTiN using aqueous hydrogen peroxide. Measurement was carried out byirradiating, with a circular electron beam having a diameter of 1 mm, onthe center of a flank face for tools having a shape according toISO/CNMG120408 and on the center of a rake face for tools having a shapeaccording to ISO/SEEN42AFTN1.

As a result, the present coated cutting tools 1-15 contained (in wt %)Al: 47.6-49.8%, O: 37.7-45.8%, Ti: 4.4-10.9%, and Cl: 0.015-0.21%.Likewise, the conventional coated cutting tools 1-10 contained Al:52.8-53.0%, O: 47.0-47.2%, Ti: 0.01-0.02%, and Cl: less than measurablelimit.

For the purpose of evaluating chipping resistance, present coatedcutting tools 1-3 and conventional coated cutting tools 1 and 2 weresubjected to an intermittent cutting test of ductile cast iron under thefollowing conditions to measure flank face wear.

Cutting material: square piece of JIS/FCD450

Cutting speed: 180 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 4-6 and conventional coated cutting tools 3and 4 were subjected to a dry intermittent cutting test of alloy steelunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/SCM440

Cutting speed: 180 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 7-9 and conventional coated cutting tools 5and 6 were subjected to a dry intermittent cutting test of carbon steelunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/S45C

Cutting speed: 180 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 10-12 and conventional coated cutting tools7 and 8 were subjected to a dry intermittent cutting test of cast ironunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/FC200

Cutting speed: 180 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev. Cutting time: 15 minutes

Present coated cutting tools 13-15 and conventional coated cutting tools9 and 10 were subjected to a dry milling cutting test (intermittentcutting) of alloy steel under the following conditions to measure flankface wear.

Cutting material: square piece of JIS/SNCM439 with a width of 100 mm anda length of 500 mm

Using condition: mounting of single tooth on cutter of 125 mm dia.

Rotation: 510 r.p.m.

Cutting speed: 200 m/min.

Cutting depth: 2 mm

Feed rate: 0.2 mm/tooth

Cutting time: 3 paths (cutting time/path: 5.3 minutes)

Tables 6 and 7 show the results of these measurements.

Example 2

Cemented carbide substrates A-E were prepared by the same method as usedin Example 1. Next, reactions 16-30 of the present invention andconventional reactions 11-20 were performed and coated cemented carbidetools (hereinafter referred to as present coated cutting tools 16-30 andconventional coated cutting tools 11-20) were manufactured by forminghard coating layers having the compositions and target layer thicknesses(at the flank face) shown in Tables 9 and 10 using conventional chemicalvapor deposition under the conditions shown in Table 2 and Table 8 (Al₂O₃ (a)-(n) in Table 8 show aluminum oxide layers and Al₂ O₃ (o) shows anAl₂ O₃ layer, which are also applicable to Tables 9 and 10).

As to each of the aluminum oxide layers and the Al₂ O₃ layers(collectively referred to in Tables 11 and 12 as Al₂ O₃ layers)constituting the hard coating layers of the various resultant coatedcutting tools, the maximum layer thickness of the cutting edge where aflank face intersected a rake face was measured and further the layerthicknesses on the flank face and the rake face which were located 1 mminward from the cutting edge were measured. Tables 11 and 12 show theresults of the measurements.

The layer thicknesses of the layers constituting the hard coating layer,other than the aluminum oxide layer and the Al₂ O₃ layer, had almost nolocal dispersion and exhibited almost the same values as target layerthicknesses.

The elemental composition of the aluminum oxide layer of the presentcoated cutting tools and that of the Al₂ O₃ layer of the conventionalcoated cutting tools were analyzed using an EPMA. Elemental analysis wascarried out according to the same procedure used in Example 1.

As a result, present coated cutting tools 16-30 contained (in wt %) Al:46.5-49.9%, O: 37.7-45.8%, Ti: 4.1-12.1%, and Cl: 0.019-0.23%. Likewise,conventional coated cutting tools 11-20 contained Al: 52.8-53.0%, O:47.0-47.2%, Ti: 0.01-0.02%, and Cl: less than measurable limit.

For the purpose of evaluating chipping resistance, present coatedcutting tools 16-18 and conventional coated cutting tools 11 and 12 weresubjected to an intermittent cutting test of ductile cast iron under thefollowing conditions to measure flank face wear.

Cutting material: square piece of JIS/FCD450

Cutting speed: 180 m/min.

Cutting depth: 2.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 19-21 and conventional coated cutting tools13 and 14 were subjected to a dry intermittent cutting test of alloysteel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/SCM440

Cutting speed: 180 m/min.

Cutting depth: 2.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 22-24 and conventional coated cutting tools15 and 16 were subjected to a dry intermittent cutting test of carbonsteel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/S45C

Cutting speed: 180 m/min.

Cutting depth: 2.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 25-27 and conventional coated cutting tools17 and 18 were subjected to a dry intermittent cutting test of cast ironunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/FC200

Cutting speed: 180 m/min.

Cutting depth: 2.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 28-30 and conventional coated cutting tools19 and 20 were subjected to a dry milling cutting test (intermittentcutting) of alloy steel under the following conditions to measure flankface wear.

Cutting material: square piece of JIS/SCM440 with a width of 100 mm anda length of 500 mm

Using condition: mounting of single tooth on cutter of 125 mm dia.

Rotation: 510 r.p.m.

Cutting speed: 200 m/min.

Cutting depth: 2 mm

Feed rate: 0.2 mm/tooth

Cutting time: 3 paths (cutting time/path: 5.3 minutes)

Tables 11 and 12 show the results of these measurements.

Example 3

Cemented carbide substrates A-E were prepared by the same method as usedin Example 1. Next, reactions 31-44 of the present invention andconventional methods 21-30 were performed, and coated cemented carbidetools (hereinafter, referred to as present coated cutting tools 31-44and conventional coating cutting tools 21-30) were manufactured byforming hard coating layers having the compositions and target layerthicknesses (at the flank face) shown in Tables 14 and 15 usingconventional chemical vapor deposition, under the conditions shown inTable 2 and Table 13 (Al₂ O₃ (a)-(l) in Table 13 show aluminum oxidelayers and Al₂ O₃ (m) shows an Al₂ O₃ layer, which are also applicableto Tables 14 and 15 likewise).

With respect to each of the aluminum oxide layers and the Al₂ O₃ layers(referred to collectively in Tables 16 and 17 as Al₂ O₃ layers)constituting the hard coating layers of the various resultant coatedcutting tools, the maximum layer thickness of the cutting edge where aflank face intersected a rake face was measured and further the layerthicknesses on the flank face and the rake face which were located 1 mminward from the cutting edge were measured. Tables 16 and 17 show theresults of the measurements.

The layer thicknesses of the layers of the hard coated layer, other thanthe aluminum oxide layer and the Al₂ O₃ layer, had almost no localdispersion and exhibited almost the same values as target layerthicknesses.

The elemental composition of the aluminum oxide layer of the presentcoated cutting tools and that of the Al₂ O₃ layer of the conventionalcoated cutting tools were analyzed using an EPMA. Elemental analysis wascarried out using the same procedure as in Example 1.

The present coated cutting tools 31-44 contained (in wt %) Al:46.6-47.8%, O: 35.5-42.8%, Ti: 6.5-14.3%, and Cl: 0.11-0.46%. Likewise,conventional coated cutting tools 21-30 contained Al: 52.8-53.0%, O:47.0-47.2%, Ti: 0.01-0.02%, and Cl: less than measurable limit.

For the purpose of evaluating chipping resistance, present coatedcutting tools 31-36 and conventional coated cutting tools 21 and 22 weresubjected to an intermittent cutting test of mild steel under thefollowing conditions to measure the flank face wear.

Cutting material: square piece of mild steel

Cutting speed: 220 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.18 mm/rev.

Cutting time: 20 minutes

Present coated cutting tools 37-38 and conventional coated cutting tools23 and 24 were subjected to a dry intermittent cutting test of ductilecast iron under the following conditions to measure the flank face wear.

Cutting material: square piece of JIS/FCD450

Cutting speed: 150 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 39 and 40 and conventional coated cuttingtools 25 and 26 were subjected to a dry intermittent cutting test ofalloy steel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/SNC/N439

Cutting speed: 150 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 41 and 42 and conventional coated cuttingtools 27 and 28 were subjected to a dry intermittent cutting test ofcarbon steel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/S45C

Cutting speed: 150 m/min.

Cutting depth: 2 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 43 and 44 and conventional coated cuttingtools 29 and 30 were subjected to a dry milling cutting test(intermittent cutting) of mild steel under the following conditions tomeasure flank face wear.

Cutting material: square piece of mild steel with a width of 100 mm anda length of 500 mm

Using condition: mounting of single tooth on cutter of 125 mm dia.

Rotation: 600 r.p.m.

Cutting speed: 280 m/min.

Cutting depth: 2 mm

Feed rate: 0.24 mm/tooth

Cutting time: 7 paths (cutting time/path: 3.6 minutes) Tables 16 and 17show the result of these measurements.

Example 4

Cemented carbide substrates A-E were prepared by the same method as usedin Example 1. Next, reactions 46-60 (45 lacked) of the present inventionand conventional reactions 31-40 were performed, and coated cementedcarbide tools (hereinafter, referred to as present coated cutting tools46-60 and conventional coated cutting tools 31-40) were manufactured byforming hard coating layers having the compositions and target layerthicknesses (at the flank face) shown in Tables 19 and 20 usingconventional chemical vapor deposition, under the conditions shown inTable 2 and Table 18 (Al₂ O₃ (a)-(l) in Table 18 show aluminum oxidelayers and Al₂ O₃ (m) shows an Al₂ O₃ layer, which are also applicableto Tables 19 and 20 likewise).

As to each of the aluminum oxide layers and the Al₂ O₃ layers(collectively referred to in Tables 21 and 22 as Al₂ O₃ layers)constituting the hard coating layers of the various resultant coatedcutting tools, the maximum layer thickness of the cutting edge where aflank face intersected a rake face was measured and further the layerthicknesses on the flank face and the rake face which were located 1 mminward from the cutting edge were measured. Tables 21 and 22 show theresult of the measurements.

The layer thicknesses of the layers constituting the hard coating layer,other than the aluminum oxide layer and the Al₂ O₃ layer, had almost nolocal dispersion and exhibited almost the same values as target layerthicknesses.

The elemental composition of the aluminum oxide layer of the presentcoated cutting tools and that of the Al₂ O₃ layer of the conventionalcoated cutting tools were analyzed using an EPMA. Elemental analysis wascarried out based on the same procedure as used in Example 1.

Present coated cutting tools 46-60 contained (in wt %) Al: 44.3-47.9%,O: 35.1-42.7%, Ti: 5.9-14.7%, and Cl: 0.14-0.41%. Likewise, conventionalcoated cutting tools 31-40 contained Al: 52.8-53.0%, 0: 47.0-47.2%, Ti:0.01-0.02%, and Cl: less than measurable limit.

For the purpose of evaluating chipping resistance, present coatedcutting tools 46-48 and conventional coated cutting tools 31 and 32 weresubjected to an intermittent cutting test of ductile cast iron under thefollowing conditions to measure flank face wear.

Cutting material: square piece of JIS/FCD450

Cutting speed: 180 m/min.

Cutting depth: 3 mm

Feed rate: 0.2 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 49-51 and conventional coated cutting tools33 and 34 were subjected to a dry intermittent cutting test of alloysteel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/SNCM439

Cutting speed: 180 m/min.

Cutting depth: 3 mm

Feed rate: 0.2 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 52-54 and conventional coated cutting tools35 and 36 were subjected to a dry intermittent cutting test of carbonsteel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/S30C

Cutting speed: 180 n/min.

Cutting depth: 3 mm

Feed rate: 0.2 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 55-57 and conventional coated cutting tools37 and 38 were subjected to a dry intermittent cutting test of cast ironunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/FC300

Cutting speed: 180 m/min.

Cutting depth: 3 mm

Feed rate: 0.2 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 58-60 and conventional coated cutting tools39 and 40 were subjected to a dry milling cutting test (intermittentcutting) of alloy steel under the following conditions to measure flankface wear.

Cutting material: square piece of JIS/SNCM439 with a width of 100 mm anda length of 500 mm

Using condition: mounting of single tooth on cutter of 125 mm dia.

Rotation: 510 r.p.m.

Cutting speed: 200 m/min.

Cutting depth: 2 mm

Feed rate: 0.2 mm/tooth

Cutting time: 3 paths (cutting time/path: 5.3 minutes) Tables 21 and, 22show the results of these measurements.

Example 5

Cemented carbide substrates A-E were prepared by the same method as usedi n Example 1. Reactions 61-75 of the present invention and conventionalmethods 41-50 performed and coated cemented carbide tools (hereinafter,referred to as present coated cutting tools 61-75 and conventionalcoated cutting tools 41-50) were manufactured by forming hard coatinglayers having the compositions and target layer thicknesses (at theflank face) shown in Tables 24 and 25 using conventional chemical vapordeposition, under the conditions shown in Table 2 and Table 23 (Al₂ O3(a)-(m) in Table 23 show aluminum oxide layers and Al₂ O₃ (n) shows anAl₂ O₃ layer, which is also applicable to Tables 24 and 25 likewise).

As to each of the aluminum oxide layers and the Al₂ O₃ layers(collectively referred to in Tables 26 and 27 as Al₂ O₃ layers)constituting the hard coated layers of the various resultant coatedcutting tools, the maximum layer thickness of the cutting edge where aflank face intersected a rake face was measured and further the layerthicknesses on the flank face and the rake face which were located 1 mminward from the cutting edge were measured. Tables 26 and 27 show theresults of the measurements.

The layer thicknesses of the layers constituting the hard coating layer,other than the aluminum oxide layer and the Al₂ O₃ layer, had almost nolocal dispersion and exhibited almost the same values as target layerthicknesses.

The elemental composition of the aluminum oxide layer of the presentcoated cutting tools and that of the Al₂ O₃ layer of the conventionalcoated cutting tools were analyzed using an EPMA. Elemental analysis wascarried out based on the same procedure as Example 1.

Present coated cutting tools 61-75 contained (in wt %) Al: 52.8-53.1%,O: 46.5-46.9%, and Cl: 0.13-0.36%. Likewise, conventional coated cuttingtools 41-50 contained Al: 52.8-53.0%, O: 47.0-47.2%, Ti: 0.01-0.02%, andCl: less than measurable limit.

For the purpose of evaluating chipping resistance, present coatedcutting tools 61-63 and conventional coated cutting tools 41 and 42 weresubjected to an intermittent cutting test of ductile cast iron under thefollowing conditions to measure flank face wear.

Cutting material: square piece of JIS/FCD450

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.35 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 64-66 and conventional coated cutting tools43 and 44 were subjected to a dry intermittent cutting test of alloysteel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/SCM440

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.35 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 67-69 and conventional coated cutting tools45 and 46 were subjected to a dry intermittent cutting test of carbonsteel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/S45C

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.35 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 70-72 and conventional coated cutting tools47 and 48 were subjected to a dry intermittent cutting test of cast ironunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/FC200

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.35 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 73-75 and conventional coated cutting tools49 and 50 were subjected to a dry milling cutting test (intermittentcutting) of alloy steel under the following conditions to measure flankface wear.

Cutting material: square piece of JIS/SNCM439 with a width of 100 mm anda length of 500 mm

Using condition: mounting of single tooth on cutter of 125 mm dia.

Rotation: 380 r.p.m.

Cutting speed: 150 m/min.

Cutting depth: 2 mm

Feed rate: 0.25 mm/tooth

Cutting time: 2 paths (cutting time/path: 5.5 minutes) Tables 26 and 27show the results of these measurements.

Example 6

Cemented carbide substrates A-E were prepared by the same method as usedin Example 1. Reactions 76-85 of the present invention and conventionalreactions 51-60 were performed and coated cemented carbide tools(hereinafter, referred to as the present coated cutting tools 76-85 andconventional coated cutting tools 51-60) were manufactured by forminghard coating layers having the compositions and target layer thicknesses(at the flank face) shown in Tables 29 and 30 using conventionalchemical vapor deposition device, under the conditions shown in Table 2and Table 28 (Al₂ O₃ (a)-(i) in Table 28 show aluminum oxide layers andAl₂ O₃ (j) shows an Al₂ O₃ layer, which are also applicable to Tables 29and 30).

As to each of the aluminum oxide layers and the Al₂ O₃ layers(collectively referred to in Tables 31 and 32 as Al₂ O₃ layers)constituting the hard coating layers of the various resultant coatedcutting tools, the maximum layer thickness of the cutting edge where aflank face intersected a rake face was measured and further the layerthicknesses on the flank face and the rake face which were located 1 mminward from the cutting edge were measured. Tables 31 and 32 show theresults of the measurements.

The layer thicknesses of the layers constituting the hard coating layer,other than the aluminum oxide layer and the Al₂ O₃ layer, had almost nolocal dispersion and exhibited almost the same values as target layerthicknesses.

The elemental composition constituting the aluminum oxide layer of thepresent coated cutting tools and that of the Al₂ O₃ layer of theconventional coated cutting tools were analyzed using an EPMA. Elementalanalysis was carried out based on the same procedure used in Example 1.

Present coated cutting tools 76-85 contained (in wt %) Al: 52.9-53.1%,O: 46.4-46.7%, and Cl: 0.45-0.47%. Likewise, the conventional coatedcutting tools 51-60 contained Al: 52.8-53.0%, O: 47.0-47.2%, Ti:0.01-0.02%, and Cl: less than measurable limit.

For the purpose of evaluating chipping resistance, present coatedcutting tools 76 and 77 and conventional coated cutting tools 51 and 52were subjected to an intermittent cutting test of ductile cast ironunder the following conditions to measure flank face wear.

Cutting material: square piece of JIS/FCD450

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 78 and 79 and conventional coated cuttingtools 53 and 54 were subjected to a dry intermittent cutting test ofalloy steel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/SCM440

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 80 and 81 and conventional coated cuttingtools 55 and 56 were subjected to a dry intermittent cutting test ofcarbon steel under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/S45C

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools 82 and 83 and conventional coated cuttingtools 57 and 58 were subjected to a dry intermittent cutting test ofcast iron under the following conditions to measure flank face wear.

Cutting material: square piece of JIS/FC200

Cutting speed: 200 m/min.

Cutting depth: 1.5 mm

Feed rate: 0.3 mm/rev.

Cutting time: 15 minutes

Present coated cutting tools of the present invention 84 and 85 andconventional coated cutting tools 59 and 60 were subjected to a drymilling cutting test (intermittent cutting) of alloy steel under thefollowing conditions to measure flank face wear.

Cutting material: square piece of JIS/SNCM439 with a width of 100 mm anda length of 500 mm

Using condition: mounting of single tooth on cutter of 125 mm dia.

Rotation: 380 r.p.m.

Cutting speed: 150 m/min.

Cutting depth: 2 mm

Feed rate: 0.2 mm/tooth

Cutting time: 2 paths (cutting time/path: 7 minutes)

Tables 31 and 32 show the result of these measurements.

                                      TABLE 1                                     __________________________________________________________________________                                  Sintering Conditions                                   Blended Composition (wt %)                                                                           Pressure                                                                          Temperature                                                                         Holding                                                                            Internal Hard-                   Type   Co (Ti,W)C                                                                            (Ti,W)CN                                                                           (Ta,Nb)C                                                                           WC   (torr)                                                                            (°C.)                                                                        Time (hr)                                                                          ness (HRA)                       __________________________________________________________________________    Cemented                                                                           A 6.3                                                                              --   6    4.1  Remainder                                                                          0.10                                                                              1380  1    90.3                             Carbide                  (Medium)                                             Substrate                                                                          B 5.3                                                                              5.2  --   5.1  Remainder                                                                          0.05                                                                              1450  1    90.9                                                      (Medium)                                                  C 9.5                                                                              8.1  --   4.9  Remainder                                                                          0.05                                                                              1380  1.5  89.9                                                      (Medium)                                                  D 4.5                                                                              --   4.8  3.1  Remainder                                                                          0.10                                                                              1410  1    91.4                                                      (Medium)                                                  E 10.2                                                                             --   --   2.2  Remainder                                                                          0.05                                                                              1380  1    89.7                                                      (Rough)                                              __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________             Hard Coating Layer Forming Conditions                                                               Reaction conditions                                                           Pressure                                                                          Temperature                                Hard Coating Layer                                                                     Composition of Reaction Gas (Vol %)                                                                 (torr)                                                                            (°C.)                               __________________________________________________________________________    TiC      TiCl.sub.4 : 4%, CH.sub.4 : 9%, H.sub.2 : Remainder                                                 50  1020                                       TiN (First layer)                                                                      TiCl.sub.4 : 4%, N.sub.2 : 30%, H.sub.2 : Remainder                                                 50  915                                        TiN (Other layer)                                                                      TiCl.sub.4 : 4%, N.sub.2 : 35%, H.sub.2 : Remainder                                                 200 1025                                       1-TiCN   TiCl.sub.4 : 4%, CH.sub.3 CN: 1.2%, N.sub.2 : 30%, H.sub.2 :                  Remainder             50  900                                        p-TiCN   TiCl.sub.4 : 4%, CH.sub.4 : 8%, N.sub.2 : 35%, H.sub.2 :                      Remainder             50  1025                                       TiO.sub.2                                                                              TiCl.sub.4 : 4%, CO.sub.2 : 6%, H.sub.2 : Remainder                                                 80  1000                                       TiCO     TiCl.sub.4 : 4%, CO: 9%, H.sub.2 : Remainder                                                        50  1000                                       TiNO     TiCl.sub.4 : 4%, NO: 9%, H.sub.2 : Remainder                                                        50  1000                                       TiCNO    TiCl.sub.4 : 4%, CO: 5%, N.sub.2 : 8%, H.sub.2 :                                                    50mainder                                                                         1000                                       __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Hard Coating Layer Forming Conditions                                         Hard Composition of Reaction Gas (Vol %)                                                                           Reaction Conditions                      Coating                AlCl.sub.3 /  Pressure                                                                          Temperature                          Layer                                                                              AlCl.sub.3                                                                       NO NO.sub.2                                                                         N.sub.2 O                                                                        TiCl.sub.4                                                                       H.sub.2                                                                          TiCl.sub.4                                                                        Ar   He   (torr)                                                                            (°C.)                         __________________________________________________________________________    Al.sub.2 O.sub.3 (a)                                                               0.5                                                                              10 -- -- 0.01                                                                             5  50  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (b)                                                               2  10 -- -- 0.1                                                                              5  20  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (c)                                                               5  10 -- -- 0.3                                                                              5  17  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (d)                                                               7  10 -- -- 0.5                                                                              5  14  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (e)                                                               10 10 -- -- 1  5  10  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (f)                                                               5   5 -- -- 0.2                                                                              3  25  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (g)                                                               5  15 -- -- 0.2                                                                              3  25  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (h)                                                               5  20 -- -- 0.2                                                                              3  25  Remainder                                                                          --   50  950                                  Al.sub.2 O.sub.3 (i)                                                               5  -- 1  -- 0.1                                                                              2  50  --   Remainder                                                                          50  950                                  Al.sub.2 O.sub.3 (j)                                                               5  -- -- 30 0.1                                                                              2  50  --   Remainder                                                                          50  950                                  Al.sub.2 O.sub.3 (k)                                                               5  10 -- -- 0.2                                                                              0.5                                                                              25  Remainder                                                                          --   20  1000                                 Al.sub.2 O.sub.3 (l)                                                               5  10 -- -- 0.2                                                                              1  25  Remainder                                                                          --   20  1000                                 Al.sub.2 O.sub.3 (m)                                                               5  10 -- -- 0.2                                                                              10 25  Remainder                                                                          --   100 930                                  Al.sub.2 O.sub.3 (n)                                                               5  10 -- -- 0.2                                                                              20 25  Remainder                                                                          --   100 900                                  Al.sub.2 O.sub.3 (o)                                                               AlCl.sub.3 : 5%, CO.sub.2 : 12%, H.sub.2 : Remainder                                                          100 1020                                 __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________           Symbol of                                                                          Hard coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                      Type   Substrate                                                                          First Layer                                                                         Second Layer                                                                         Third Layer                                                                         Fourth Layer                                                                        Fifth Layer                                                                          Sixth Layer                       __________________________________________________________________________    Method of                                                                          1 A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                         Al.sub.2 O.sub.3 (a)(3)                                                             TiN (0.3)                                                                            --                                Present                                                                            2 A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                         Al.sub.2 O.sub.3 (b)(6)                                                             TiN (0.3)                                                                            --                                Invention                                                                          3 A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                         Al.sub.2 O.sub.3 (c)(9)                                                             TiN (0.3)                                                                            --                                     4 B    p-TiCN (8)                                                                          Al.sub.2 O.sub.3 (c)(5)                                                              TiN (0.3)                                                                           --    --     --                                     5 B    TiC (8)                                                                             TiCO (0.2)                                                                           Al.sub.3 O.sub.3 (d)(5)                                                             TiN (0.3)                                                                           --     --                                     6 B    TiC (8)                                                                             TiNO (0.2)                                                                           Al.sub.2 O.sub.3 (e)(5)                                                             --    --     --                                     7 C    TiC (2)                                                                             TiN (1)                                                                              p-TiCN (4)                                                                          TiO.sub.2 (0.1)                                                                     Al.sub.2 O.sub.3 (f)(2)                                                              --                                     8 C    TiC (2)                                                                             TiN (1)                                                                              p-TiCN (4)                                                                          TiNO (0.1)                                                                          Al.sub.2 O.sub.3 (g)(4)                                                              --                                     9 C    TiC (2)                                                                             TiN (1)                                                                              p-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (h)(6)                                                              --                                     10                                                                              D    TiC (0.1)                                                                           TiN (0.2)                                                                            1-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (i)(6)                                                              TiN (0.2)                              11                                                                              D    TiC (0.1)                                                                           TiN (0.2)                                                                            1-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (j)(9)                                                              TiN (0.2)                              12                                                                              D    TiC (0.1)                                                                           TiN (0.2)                                                                            1-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (k)(12)                                                             TiN (0.2)                              13                                                                              E    TiC (0.5)                                                                           Al.sub.2 O.sub.3 (1)(2.5)                                                            --    --    --     --                                     14                                                                              E    TiN (0.1)                                                                           i-TiCN (1)                                                                           p-TiCN (0.1)                                                                        Al.sub.2 O.sub.3 (m)(2)                                                             TiN (0.1)                                                                            --                                     15                                                                              E    p-TiN (0.5)                                                                         Al.sub.2 O.sub.3 (n)(2)                                                              TiN (0.1)                                                                           --    --     --                                __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________           Symbol of                                                                          Hard coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                      Type   Substrate                                                                          First Layer                                                                         Second Layer                                                                         Third Layer                                                                         Fourth Layer                                                                        Fifth Layer                                                                          Sixth Layer                       __________________________________________________________________________    Conven-                                                                            1 A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                         Al.sub.2 O.sub.3 (o)(6)                                                             TiN (0.3)                                                                            --                                tional                                                                             2 A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                         Al.sub.2 O.sub.3 (o)(9)                                                             TiN (0.3)                                                                            --                                Method                                                                             3 B    p-TiCN (8)                                                                          Al.sub.2 O.sub.3 (o)(5)                                                              TiN (0.3)                                                                           --    --     --                                     4 B    TiC (8)                                                                             TiNO (0.2)                                                                           Al.sub.2 O.sub.3 (o)(5)                                                             --    --     --                                     5 C    TiC (2)                                                                             TiN (1)                                                                              p-TiCN (4)                                                                          TiNO (0.1)                                                                          Al.sub.2 O.sub.3 (o)(4)                                                              --                                     6 C    TiC (2)                                                                             TiN (1)                                                                              p-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (o)(6)                                                              --                                     7 D    TiC (0.1)                                                                           TiN (0.2)                                                                            1-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (o)(9)                                                              TiN (0.2)                              8 D    TiC (0.1)                                                                           TiN (0.2)                                                                            1-TiCN (4)                                                                          TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (o)(12)                                                             TiN (0.2)                              9 E    TiC (0.5)                                                                           Al.sub.2 O.sub.3 (o)(2.5)                                                            --    --    --     --                                     10                                                                              E    TiN (0.1)                                                                           1-TiCN (1)                                                                           p-TiCN (0.1)                                                                        Al.sub.2 O.sub.3 (o)(2)                                                             TiN (0.1)                                                                            --                                __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                                  Al.sub.2 O.sub.3 Layer (Layer Thick-                                          ness of Each Portion: μm)                                                    Flank  Cutting        Wear of Flank Face                          Type        Face   Edge    Rake Face                                                                            (mm)                                        ______________________________________                                        Hard-Material-                                                                          1     3.0    3.5   2.8    0.21                                      Coated Cemented                                                                         2     6.0    6.9   5.8    0.26                                      Carbide Cutting                                                                         3     9.0    10.4  8.5    0.27                                      Tool of Present                                                                         4     5.1    6.0   5.0    0.23                                      Invention 5     5.0    5.7   4.6    0.23                                                6     5.0    5.6   4.7    0.22                                                7     2.0    2.3   1.9    0.20                                                8     4.0    4.5   3.9    0.21                                                9     5.9    7.0   5.6    0.22                                                10    6.0    6.9   5.9    0.28                                                11    9.0    10.5  8.6    0.30                                                12    12.1   14.0  11.3   0.31                                                13    2.5    2.9   2.4    0.19                                                14    2.0    2.2   1.9    0.19                                                15    2.0    2.3   2.0    0.20                                      ______________________________________                                    

                                      TABLE 7                                     __________________________________________________________________________                Al.sub.2 O.sub.3 Layer (Layer                                                 Thickness of                                                                  Each Portion: μm)                                                          Flank                                                                            Cutting                                                                           Rake                                                                             Wear of Flank Face                                      Type        Face                                                                             Edge                                                                              Face                                                                             (mm)                                                    __________________________________________________________________________    Conventional Hard-                                                                     1  6.0                                                                              10.1                                                                              2.6                                                                              Usable Life Finished in 2.5 min.                        Material-Coated                                                                        2  8.8                                                                              15.1                                                                              3.9                                                                              Usable Life Finished in 3.0 min.                        Cemented Carbide                                                                       3  4.8                                                                              10.0                                                                              2.2                                                                              Usable Life Finished in 4.5 min.                        Cutting Tool                                                                           4  4.9                                                                              9.1 2.5                                                                              Usable Life Finished in 4.5 min.                                 5  3.9                                                                              6.9 2.0                                                                              Usable Life Finished in 6.5 min.                                 6  6.0                                                                              10.3                                                                              3.1                                                                              Usable Life Finished in 8.0 min.                                 7  8.7                                                                              15.1                                                                              4.1                                                                              Usable Life Finished in 2.0 min.                                 8  11.5                                                                             20.4                                                                              4.9                                                                              Usable Life Finished in 2.5 min.                                 9  2.5                                                                              4.1 1.3                                                                              Usable Life Finished in 11.5 min.                                1  2.0                                                                              3.9 1.2                                                                              Usable Life Finished in 8.0 min.                                 0                                                                    __________________________________________________________________________     (Usable life is finished due to chipping.)                               

                                      TABLE 8                                     __________________________________________________________________________    Hard Coating Layer Forming Conditions                                         Hard Composition of Reaction Gas (Vol %)                                                                             Reaction Conditions                    Coating                  AlCl.sub.3 /  Pressure                                                                          Temperature                        Layer                                                                              AlCl.sub.3                                                                       NO NO.sub.2                                                                         N.sub.2 O                                                                        TiCl.sub.4                                                                       H.sub.2                                                                          N.sub.2                                                                         TiCl.sub.4                                                                        Ar   He   (torr)                                                                            (°C.)                       __________________________________________________________________________    Al.sub.2 O.sub.3 (a)                                                               0.5                                                                              3  -- -- 0.02                                                                             5  5 25  Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (b)                                                               2  5  -- -- 0.02                                                                             5  5 100 Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (c)                                                               5  10 -- -- 0.1                                                                              5  5 50  Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (d)                                                               7  15 -- -- 0.1                                                                              5  5 70  Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (e)                                                               10 20 -- -- 1  5  5 10  Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (f)                                                               3  -- 1  -- 0.3                                                                              5  5 10  Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (g)                                                               3  -- -- 30 0.3                                                                              5  5 10  Remainder                                                                          --   50  960                                Al.sub.2 O.sub.3 (h)                                                               3  10 -- -- 0.2                                                                              0.5                                                                              7 15  --   Remainder                                                                          100 900                                Al.sub.2 O.sub.3 (i)                                                               3  10 -- -- 0.2                                                                              1  7 15  --   Remainder                                                                          100 900                                Al.sub.2 O.sub.3 (j)                                                               3  10 -- -- 0.2                                                                              10 7 15  --   Remainder                                                                          100 900                                Al.sub.2 O.sub.3 (k)                                                               3  10 -- -- 0.2                                                                              20 7 15  --   Remainder                                                                          100 900                                Al.sub.2 O.sub.3 (l)                                                               3  15 -- -- 0.05                                                                             10 1 60  Remainder                                                                          --   30  1000                               Al.sub.2 O.sub.3 (m)                                                               3  15 -- -- 0.05                                                                             10 10                                                                              60  Remainder                                                                          --   30  1000                               Al.sub.2 O.sub.3 (n)                                                               3  15 -- -- 0.05                                                                             10 15                                                                              60  Remainder                                                                          --   30  1000                               Al.sub.2 O.sub.3 (o)                                                               AlCl.sub.3 : 5%, CO.sub.2 : 12%, H.sub.2 : Remainder                                                            100 1020                               __________________________________________________________________________

                                      TABLE 9                                     __________________________________________________________________________                Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                             Symbol of                                                                          First Second Third  Fourth Fifth  Sixth                           Type   Substrate                                                                          Layer Layer  Layer  Layer  Layer  Layer                           __________________________________________________________________________    Method of                                                                          16                                                                              A    TiC (3)                                                                             TiN (3)                                                                              TiC (1)                                                                              TiCNO (0.1)                                                                          Al.sub.2 O.sub.3                                                                     TiN (0.2)                       Present                                                                            17                                                                              A    TiN (0.3                                                                            1-TiCN (6)                                                                           TiC (2)                                                                              TiCO (0.1)                                                                           Al.sub.2 O.sub.3                                                                     TiN (0.2)                       Invention                                                                          18                                                                              A    TiN (0.3)                                                                           1-TiCN (8)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (c)(3)                                                              TiN (0.2)                                                                            --                                   19                                                                              B    TiN (0.3)                                                                           1-TiCN (8)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (c)(5)                                                              TiN (0.2)                                                                            --                                   20                                                                              B    p-TiCN (8)                                                                          Al.sub.2 O.sub.3 (d)(5)                                                              TiN (0.2)                                                                            --     --     --                                   21                                                                              B    p-TiCN (8)                                                                          TiNO (0.1)                                                                           Al.sub.2 O.sub.3 (a)(5)                                                              TiN (0.2)                                                                            --     --                                   22                                                                              C    TiC (6)                                                                             Al.sub.2 O.sub.3 (f)(4)                                                              TiN (0.2)                                                                            --     --     --                                   23                                                                              C    p-TiCN (6)                                                                          TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (g)(6)                                                              TiN (0.2)                                                                            --     --                                   24                                                                              C    TiN (0.3)                                                                           1-TiCN (6)                                                                           p-TiCN (0.1)                                                                         Al.sub.2 O.sub.3 (h)(6)                                                              --     --                                   25                                                                              D    TiN (0.2)                                                                           1-TiCN (5)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (i)(8)                                                              TiN (0.2)                                                                            --                                   26                                                                              D    p-TiCN (5)                                                                          TiCO (0.1)                                                                           Al.sub.2 O.sub.3 (j)(8)                                                              --     --     --                                   27                                                                              D    TiC (3)                                                                             p-TiCN (1)                                                                           Al.sub.2 O.sub.3 (k)(10)                                                             --     --     --                                   28                                                                              E    TiC (0.5)                                                                           TiN (1)                                                                              Al.sub.2 O.sub.3 (l)(2)                                                              TiN (0.1)                                                                            --     --                                   29                                                                              E    TiC (0.5)                                                                           Al.sub.2 O.sub.3 (m)(2.5)                                                            --     --     --     --                                   30                                                                              E    TiN (0.2)                                                                           1-TiCN (0.5)                                                                         TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (n) (2)                                                             TiN (0.2)                                                                            --                              __________________________________________________________________________

                                      TABLE 10                                    __________________________________________________________________________                Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                             Symbol of                                                                          First Second Third  Fourth Fifth  Sixth                           Type   Substrate                                                                          Layer Layer  Layer  Layer  Layer  Layer                           __________________________________________________________________________    Conven-                                                                            11                                                                              A    TiC (3)                                                                             TiN (3)                                                                              TiC (1)                                                                              TiCNO (0.1)                                                                          Al.sub.2 O.sub.3                                                                     TiN (0.2)                       tional                                                                             12                                                                              A    TiN (0.3)                                                                           1-TiCN (8)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (o)(3)                                                              TiN (0.2)                                                                            --                              Method                                                                             13                                                                              B    TiN (0.3)                                                                           1-TiCN (8)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (o)(5)                                                              TiN (0.2)                                                                            --                                   14                                                                              B    p-TiCN (8)                                                                          Al.sub.2 O.sub.3 (o)(5)                                                              TiN (0.2)                                                                            --     --     --                                   15                                                                              C    TiC (6)                                                                             Al.sub.2 O.sub.3 (o) (4)                                                             TiN (0.2)                                                                            --     --     --                                   16                                                                              C    p-TiCN (6)                                                                          TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (o)(6)                                                              TiN (0.2)                                                                            --     --                                   17                                                                              D    p-TiCN (5)                                                                          TiCO (0.1)                                                                           Al.sub.2 O.sub.3 (o)(8)                                                              --     --     --                                   18                                                                              D    TiC (3)                                                                             p-TiCN (1)                                                                           Al.sub.2 O.sub.3 (o)(10)                                                             --     --     --                                   19                                                                              E    TiC (0.5)                                                                           Al.sub.2 O.sub.3 (o)(2.5)                                                            --     --     --     --                                   20                                                                              E    TiN (0.2)                                                                           1-TiCN (0.5)                                                                         TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (o)(2)                                                              TiN (0.2)                                                                            --                              __________________________________________________________________________

                  TABLE 11                                                        ______________________________________                                                     Al.sub.2 O.sub.3 Layer (Layer Thick-                                          ness of Each Portion: μm)                                                                Wear of                                                           Flank   Cutting Rake  Flank Face                               Type           Face    Edge    Face  (mm)                                     ______________________________________                                        Hard-Material-Coated                                                                       16    3.0     3.3   2.8   0.27                                   Cemented Carbide                                                                           17    3.0     3.4   2.7   0.23                                   Cutting Tool of Present                                                                    18    3.0     3.4   2.8   0.26                                   Invention    19    4.9     5.7   4.6   0.26                                                20    5.0     5.7   4.6   0.22                                                21    5.0     5.7   4.8   0.27                                                22    4.0     4.6   3.9   0.27                                                23    6.1     6.9   5.7   0.27                                                24    6.1     6.9   5.8   0.26                                                25    8.1     9.3   7.5   0.25                                                26    8.0     9.0   7.7   0.26                                                27    10.0    11.5  9.4   0.29                                                28    2.0     2.2   1.9   0.24                                                29    2.5     3.0   2.4   0.26                                                30    2.0     2.3   1.9   0.24                                   ______________________________________                                    

                                      TABLE 12                                    __________________________________________________________________________               Al.sub.2 O.sub.3 Layer (Layer Thickness                                       of Each Portion: μm)                                            Type       Flank Face                                                                          Cutting Edge                                                                        Rake Face                                                                          Wear of Flank Face (mm)                           __________________________________________________________________________    Conventional Hard-                                                                     11                                                                              3.0   4.6   1.5  Usable Life Finished in 4.5 min.                  Material-Coated                                                                        12                                                                              3.0   4.5   1.3  Usable Life Finished in 4.0 min.                  Cement Carbide                                                                         13                                                                              4.8   8.2   2.4  Usable Life Finished in 2.0 min.                  Cutting Tool                                                                           14                                                                              4.9   8.0   3.0  Usable Life Finished in 2.5 min.                           15                                                                              3.9   7.7   2.1  Usable Life Finished in 6.5 min.                           16                                                                              6.0   10.3  2.4  Usable Life Finished in 7.5 min.                           17                                                                              7.8   14.1  4.0  Usable Life Finished in 3.0 min.                           18                                                                              9.8   18.9  4.4  Usable Life Finished in 5.5 min.                           19                                                                              2.5   4.2   1.2  Usable Life Finished in 7.5 min.                           20                                                                              1.9   3.4   0.9  Usable Life Finished in 8.0                       __________________________________________________________________________                                min.                                               (Usable life is finished due to chipping.)                               

                                      TABLE 13                                    __________________________________________________________________________    Hard Coating Layer Forming Conditions                                         Hard                                Reaction Conditions                       Coating                                                                            Composition of Reaction Gas (Vol %)                                                                          Pressure                                                                          Temperature                           Layer                                                                              AlCl.sub.3                                                                       NO NO.sub.2                                                                         N.sub.2 O                                                                        TiCl.sub.4                                                                       AlCl.sub.3 /TiCl.sub.4                                                              Ar   He   (torr)                                                                            (°C.)                          __________________________________________________________________________    Al.sub.2 O.sub.3 (a)                                                               0.5                                                                              1  -- -- 0.01                                                                             50    Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (b)                                                               2  8  -- -- 0.1                                                                              20    Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (c)                                                               5  15 -- -- 0.3                                                                              17    Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (d)                                                               7  22 -- -- 0.6                                                                              12    Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (e)                                                               10 30 -- -- 1  10    Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (f)                                                               10 -- 30 -- 0.1                                                                              100   Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (g)                                                               5  -- -- 30 0.1                                                                              50    Remainder                                                                          --   50  1000                                  Al.sub.2 O.sub.3 (h)                                                               5  15 -- -- 0.3                                                                              17    --   Remainder                                                                          50  1000                                  Al.sub.2 O.sub.3 (i)                                                               5     15 -- 0.3                                                                              17    Remainder                                                                          --   50  900                                   Al.sub.2 O.sub.3 (j)                                                               5     -- 15 0.3                                                                              17    Remainder                                                                          --   50  1100                                  Al.sub.2 O.sub.3 (k)                                                               5  15 -- -- 0.3                                                                              17    Remainder                                                                          --   20  1000                                  Al.sub.2 O.sub.3 (l)                                                               5  15 -- -- 0.3                                                                              17    Remainder                                                                          --   200 1000                                  Al.sub.2 O.sub.3 (m)                                                               AlCl.sub.3 : 5%, CO.sub.2 : 12%, H.sub.2 : Remainder                                                         100 1020                                  __________________________________________________________________________

                                      TABLE 14                                    __________________________________________________________________________                Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                             Symbol of                                                                          First                                                                              Second                                                                              Third Fourth Fifth  Sixth  Seventh                     Type   Substrate                                                                          Layer                                                                              Layer Layer Layer  Layer  Layer  Layer                       __________________________________________________________________________    Method of                                                                          31                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (a)(6)                                                              TiN (0.3)                                                                            --     --                          Present                                                                            32                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (b)(6)                                                              TiN (0.3)                                                                            --     --                          Invention                                                                          33                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (c)(6)                                                              --     --     --                               34                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (c)(6)                                                              TiN (0.3)                                                                            --     --                               35                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (d)(6)                                                              TiN (0.3)                                                                            --     --                               36                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (e)(6)                                                              TiN (0.3)                                                                            --     --                               37                                                                              A    TiN (0.5)                                                                          1-TiCN (2)                                                                          TiC (2)                                                                             TIN (0.2)                                                                            AL.sub.2 O.sub.3 (f)(8)                                                              TiN (0.3)                                                                            --                               38                                                                              A    TiN (0.5)                                                                          1-TiCN (2)                                                                          TiC (2)                                                                             TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (g)(8)                                                              TiN (0.3)                                                                            --                               39                                                                              B    TiC (1)                                                                            p-TiCN (1.5)                                                                        TIC (1.5)                                                                           TiNO (0.1)                                                                           Al.sub.2 O.sub.3 (h)(6)                                                              --     --                               40                                                                              B    TiC (1)                                                                            p-TiCN (1.5)                                                                        TiC (1.5)                                                                           TiCO (0.1)                                                                           Al.sub.2 O.sub.3 (i)(8)                                                              --     --                               41                                                                              C    TiC (1)                                                                            p-TiCN (3)                                                                          TiCO (0.2)                                                                          Al.sub.2 O.sub.3 (j)(10)                                                             --     --     --                               42                                                                              C    TiC (1)                                                                            p-TiCN (0.5)                                                                        1-TiCN (2.5)                                                                        TiC (0.5)                                                                            p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.3)                        43                                                                              E    TiN (0.5)                                                                          1-TiCN (1)                                                                          TiNO (0.1)                                                                          Al.sub.2 O.sub.3 (l)(1.5)                                                            TiN (0.3)                                                                            --     --                               44                                                                              E    TiC (0.3)                                                                          TiN (0.3)                                                                           TiC (0.3)                                                                           TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (c)(2.5)                                                            TiN (0.2)                                                                            --                          __________________________________________________________________________

                                      TABLE 15                                    __________________________________________________________________________                Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                             Symbol of                                                                          First                                                                              Second                                                                              Third Fourth Fifth  Sixth  Seventh                     Type   Substrate                                                                          Layer                                                                              Layer Layer Layer  Layer  Layer  Layer                       __________________________________________________________________________    Conven-                                                                            21                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (m)(6)                                                              --     --     --                          tional                                                                             22                                                                              D    TiN (0.5)                                                                          1-TiCN (4.5)                                                                        TiCNO (0.1)                                                                         Al.sub.2 O.sub.3 (m)(6)                                                              TiN (0.3)                                                                            --     --                          Method                                                                             23                                                                              A    TiN (0.5)                                                                          1-TiCN (2)                                                                          TiC (2)                                                                             TiN (0.2)                                                                            Al.sub.2 O.sub.3 (m)(8)                                                              TiN (0.3)                                                                            --                               24                                                                              A    TiN (0.5)                                                                          1-TiCN (2)                                                                          TiC (2)                                                                             TiO.sub.2 (0.2)                                                                      Al.sub.2 O.sub.3 (m)(8)                                                              TiN (0.3)                                                                            --                               25                                                                              B    TiC (1)                                                                            p-TiCN (1.5)                                                                        TiC (1.5)                                                                           TiNO (0.1)                                                                           Al.sub.2 O.sub.3 (m)(8)                                                              --     --                               26                                                                              B    TiC (1)                                                                            p-TiCN (1.5)                                                                        TiC (1.5)                                                                           TiCO (0.1)                                                                           Al.sub.2 O.sub.3 (m)(8)                                                              --     --                               27                                                                              C    TiC (1)                                                                            p-TiCN (3)                                                                          TiCO (0.2)                                                                          Al.sub.2 O.sub.3 (m)(10)                                                             --     --     --                               28                                                                              C    TiC (1)                                                                            p-TiCN (0.5)                                                                        1-TiCN (2.5)                                                                        TiC (0.5)                                                                            p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.3)                        29                                                                              E    TiN (0.5)                                                                          1-TiCN (1)                                                                          TiCO (0.1)                                                                          Al.sub.2 O.sub.3 (m)(1.5)                                                            TiN (0.3)                                                                            --     --                               30                                                                              E    TIC (0.3)                                                                          TiN (0.3)                                                                           TiC (0.3)                                                                           TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (m)(2.5)                                                            TiN (0.2)                                                                            --                          __________________________________________________________________________

                  TABLE 16                                                        ______________________________________                                                     Al.sub.2 O.sub.3 Layer (Layer Thick-                                          ness of Each Portion: μm)                                                                Wear of                                                           Flank   Cutting Rake  Flank Face                               Type           Face    Edge    Face  (mm)                                     ______________________________________                                        Hard-Material-                                                                           31      5.9     7.0   5.4   0.19                                   Coated Cemented                                                                          32      5.8     6.8   5.4   0.19                                   Carbide Cutting                                                                          33      6.1     6.9   6.0   0.18                                   Tool of Present                                                                          34      6.2     7.0   6.0   0.17                                   Invention  35      6.2     7.3   6.0   0.17                                              36      6.2     7.3   5.8   0.18                                              37      8.2     9.5   7.7   0.26                                              38      7.9     9.2   7.3   0.25                                              39      8.0     9.1   7.6   0.30                                              40      7.8     9.0   7.3   0.27                                              41      10.2    12.0  9.6   0.21                                              42      9.9     11.6  9.6   0.23                                              43      1.5     1.8   1.5   0.20                                              44      2.5     3.0   2.4   0.18                                   ______________________________________                                    

                                      TABLE 17                                    __________________________________________________________________________                 Al.sub.2 O.sub.3 Layer (Layer Thickness                                       of Each Portion: μm)                                          Type         Flank Face                                                                          Cutting Edge                                                                        Rake Face                                                                          Wear of Flank Face (mm)                         __________________________________________________________________________    Conventional Hard-                                                                       21                                                                              6.2   15.0  2.9  Usable Life Finished in 1.5 min.                Material-Coated Cement                                                                   22                                                                              6.0   14.5  2.8  Usable Life Finished in 2.2 min.                Carbide Cutting Tool                                                                     23                                                                              7.8   19.1  3.3  Usable Life Finished in 7.0 min.                           24                                                                              8.1   20.0  3.7  Usable Life Finished in 5.8 min.                           25                                                                              8.2   19.8  3.6  Usable Life Finished in 9.0 min.                           26                                                                              8.1   19.7  3.5  Usable Life Finished in 6.5 min.                           27                                                                              10.1  25.2  4.5  Usable Life Finished in 11.2 min.                          28                                                                              10.3  25.5  4.6  Usable Life Finished in 11.0 min.                          29                                                                              1.5   3.8   0.7  Usable Life Finished in 13.2 min.                          30                                                                              2.4   6.1   1.2  Usable Life Finished in 12.7                    __________________________________________________________________________                                  min.                                             (Usable life is finished due to chipping.)                               

                                      TABLE 18                                    __________________________________________________________________________    Hard Coating Layer Forming Conditions                                         Hard                                  Reaction Conditions                     Coating                                                                            Composition of Reaction Gas (Vol %)                                                                            Pressure                                                                          Temperature                         Layer                                                                              AlCl.sub.3                                                                       NO NO.sub.2                                                                         N.sub.2 O                                                                        TiCl.sub.4                                                                       N.sub.2                                                                         AlCl.sub.3 /TiCl.sub.4                                                              Ar   He   (torr)                                                                            (°C.)                        __________________________________________________________________________    Al.sub.2 O.sub.3 (a)                                                               0.5                                                                              2  -- -- 0.01                                                                             7 50    Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (b)                                                               2  5  -- -- 0.05                                                                             7 40    Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (c)                                                               5  10 -- -- 0.3                                                                              7 17    Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (d)                                                               7  15 -- -- 0.3                                                                              7 23    Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (e)                                                               10 25 -- -- 1  7 10    Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (f)                                                               3  5  -- -- 0.03                                                                             5 100   Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (g)                                                               3  20 -- -- 0.03                                                                             5 100   Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (h)                                                               3  -- 1  -- 0.03                                                                             5 100   Remainder                                                                          --   50  930                                 Al.sub.2 O.sub.3 (i)                                                               3  -- -- 30 0.1                                                                              5 30    --   Remainder                                                                          50  960                                 Al.sub.2 O.sub.3 (j)                                                               3  -- -- 20 0.1                                                                              1 30    --   Remainder                                                                          50  960                                 Al.sub.2 O.sub.3 (k)                                                               3  -- -- 20 0.1                                                                              10                                                                              30    --   Remainder                                                                          50  960                                 Al.sub.2 O.sub.3 (l)                                                               3  -- -- 20 0.1                                                                              15                                                                              30    --   Remainder                                                                          50  960                                 Al.sub.2 O.sub.3 (m)                                                               AlCl.sub.3 : 5%, CO.sub.2 : 12%, H.sub.2 : Remainder                                                           100 1020                                __________________________________________________________________________

                                      TABLE 19                                    __________________________________________________________________________                Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                             Symbol of                                                                          First Second Third  Fourth Fifth  Sixth                           Type   Substrate                                                                          Layer Layer  Layer  Layer  Layer  Layer                           __________________________________________________________________________    Method of                                                                          46                                                                              A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (a)(3)                                                              TiN (0.2)                                                                            --                              Present                                                                            47                                                                              A    p-TiCN (9)                                                                          Al.sub.2 O.sub.3 (b)(3)                                                              TiN (0.2)                                                                            --     --     --                              Invention                                                                          48                                                                              A    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiC (3)                                                                              p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.2)                            49                                                                              B    TiC (5)                                                                             TiCO (0.1)                                                                           Al.sub.2 O.sub.3 (c)(5)                                                              --     --     --                                   50                                                                              B    TiC (5)                                                                             TiNO (0.1)                                                                           Al.sub.2 O.sub.3 (c)(7)                                                              --     --     --                                   51                                                                              B    p-TiCN (5)                                                                          TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (c)(7)                                                              TiN (0.2)                                                                            --     --                                   52                                                                              C    TiN (0.2)                                                                           1-TiCN (5)                                                                           TiC (2)                                                                              p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.2)                            53                                                                              C    TiN (0.2)                                                                           1-TiCN (5)                                                                           TiC (2)                                                                              p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.2)                            54                                                                              C    TiN (0.2)                                                                           1-TiCN (5)                                                                           TiC (2)                                                                              p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.2)                            55                                                                              D    TiN (0.2)                                                                           1-TiCN (6)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (g)(6)                                                              TiN (0.2)                                                                            --                                   56                                                                              D    TiN (0.2)                                                                           1-TiCN (6)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (h)(6)                                                              --     --                                   57                                                                              D    TiN (0.2)                                                                           1-TiCN (6)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (i)(10)                                                             TiN (0.2)                                                                            --                                   58                                                                              E    TiC (1)                                                                             Al.sub.2 O.sub.3 (j)(2)                                                              TiN (0.1)                                                                            --     --     --                                   59                                                                              E    TiN (0.1)                                                                           1-TiCN (1)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (k)(2)                                                              TiN (0.1)                                                                            --                                   60                                                                              E    p-TiCN (0.3)                                                                        Al.sub.2 O.sub.3 (l)(2.5)                                                            TiN (0.2)                                                                            --     --     --                              __________________________________________________________________________

                                      TABLE 20                                    __________________________________________________________________________                Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                             Symbol of                                                                          First Second Third  Fourth Fifth  Sixth                           Type   Substrate                                                                          Layer Layer  Layer  Layer  Layer  Layer                           __________________________________________________________________________    Conven-                                                                            31                                                                              A    TiN (0.3)                                                                           1-TiCN (9)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (m)(3)                                                              TiN (0.2)                                                                            --                              tional                                                                             32                                                                              A    p-TiCN (9)                                                                          Al.sub.2 O.sub.3 (m)(3)                                                              TiN (0.2)                                                                            --     --     --                              Method                                                                             33                                                                              B    TiN (5)                                                                             TiCO (0.1)                                                                           Al.sub.2 O.sub.3 (m)(5)                                                              --     --     --                                   34                                                                              B    p-TiCN (5)                                                                          TiO.sub.2 (0.1)                                                                      Al.sub.2 O.sub.3 (m)(7)                                                              TiN (0.2)                                                                            --     --                                   35                                                                              C    TiN (0.2)                                                                           1-TiCN (5)                                                                           TiC (2)                                                                              p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.2)                            36                                                                              C    TiN (0.2)                                                                           1-TiCN (5)                                                                           TiC (2)                                                                              p-TiCN (0.2)                                                                         Al.sub.2 O.sub.3                                                                     TiN (0.2)                            37                                                                              D    TiN (0.2)                                                                           1-TiCN (6)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (m)(6)                                                              --     --                                   38                                                                              D    TiN (0.2)                                                                           1-TiCN (6)                                                                           TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (m)(10)                                                             TiN (0.2)                                                                            --                                   39                                                                              E    TiN (0.1)                                                                           1-TiCN (1)                                                                           TiCNO (0.1)                                                                          Al.sub.2 O.sub.3 (m)(2)                                                              TiN (0.1)                                                                            --                                   40                                                                              E    p-TiCN (0.3)                                                                        Al.sub.2 O.sub.3 (m)(2.5)                                                            TiN (0.2)                                                                            --     --     --                              __________________________________________________________________________

                  TABLE 21                                                        ______________________________________                                                     Al.sub.2 O.sub.3 Layer (Layer Thick-                                          ness of Each Portion: μm)                                                                Wear of                                                           Flank   Cutting Rake  Flank Face                               Type           Face    Edge    Face  (mm)                                     ______________________________________                                        Hard-Material-                                                                           46      3.0     3.5   2.8   0.27                                   Coated Cemented                                                                          47      3.0     3.4   2.9   0.20                                   Carbide Cutting                                                                          48      3.0     3.4   2.9   0.22                                   Tool of Present                                                                          49      5.1     5.7   4.8   0.29                                   Invention  50      7.0     7.9   6.7   0.28                                              51      7.1     7.9   6.9   0.25                                              52      4.0     4.4   3.9   0.22                                              53      5.9     7.0   5.6   0.19                                              54      7.9     9.1   7.4   0.24                                              55      6.0     6.8   5.8   0.30                                              56      5.9     7.0   5.7   0.27                                              57      10.1    11.4  9.9   0.27                                              58      2.0     2.2   1.9   0.21                                              59      2.0     2.2   2.0   0.24                                              60      2.5     2.9   2.3   0.22                                   ______________________________________                                    

                                      TABLE 22                                    __________________________________________________________________________                 Al.sub.2 O.sub.3 Layer (Layer Thickness                                       of Each Portion: μm)                                          Type         Flank Face                                                                          Cutting Edge                                                                        Rake Face                                                                          Wear of Flank Face (mm)                         __________________________________________________________________________    Conventional Hard-                                                                       31                                                                              3.0   4.7   1.3  Usable Life Finished in 3.5 min.                Material-Coated                                                                          32                                                                              2.9   5.0   1.6  Usable Life Finished in 2.5 min.                Cement Carbide                                                                           33                                                                              5.0   9.1   2.6  Usable Life Finished in 2.0 min.                Cutting Tool                                                                             34                                                                              6.9   12.0  3.8  Usable Life Finished in 3.5 min.                           35                                                                              6.0   11.1  2.9  Usable Life Finished in 6.0 min.                           36                                                                              7.8   13.7  3.7  Usable Life Finished in 6.0 min.                           37                                                                              5.9   10.4  2.7  Usable Life Finished in 2.0 min.                           38                                                                              9.6   16.6  5.0  Usable Life Finished in 2.5 min.                           39                                                                              2.0   3.3   1.2  Usable Life Finished in 7.5 min.                           40                                                                              2.5   4.2   1.2  Usable Life Finished in 9.0                     __________________________________________________________________________                                  min.                                             (Usable life is finished due to chipping.)                               

                                      TABLE 23                                    __________________________________________________________________________    Hard Coating Layer Forming Conditions                                         Hard                          Reaction Conditions                             Coating                                                                            Composition of Reaction Gas (Vol %)                                                                    Pressure                                                                          Tempera-ture                                Layer                                                                              AlCl.sub.3                                                                       NO NO.sub.2                                                                         N.sub.2 O                                                                        H.sub.2                                                                          Ar   He   (torr)                                                                            (°C.)                                __________________________________________________________________________    Al.sub.2 O.sub.3 (a)                                                               0.5                                                                              10 -- -- 5  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (b)                                                               2  10 -- -- 5  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (c)                                                               5  10 -- -- 5  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (d)                                                               7  10 -- -- 5  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (e)                                                               10 10 -- -- 5  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (f)                                                               3  -- 1  -- 3  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (g)                                                               3   5 -- -- 3  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (h)                                                               3  -- -- 20 3  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (i)                                                               3  -- -- 30 3  Remainder                                                                          --   50  1030                                        Al.sub.2 O.sub.3 (j)                                                               5  -- -- 20 0.5                                                                              --   Remainder                                                                          50  1030                                        Al.sub.2 O.sub.3 (k)                                                               5  -- -- 20 1  --   Remainder                                                                          50  1030                                        Al.sub.2 O.sub.3 (l)                                                               5  -- -- 20 10 --   Remainder                                                                          50  1030                                        Al.sub.2 O.sub.3 (m)                                                               5  -- -- 20 20 --   Remainder                                                                          50  1030                                        Al.sub.2 O.sub.3 (n)                                                               AlCl.sub.3 : 4%, CO.sub.2 : 12%, H.sub.2 : Remainder                                                   50  1000                                        __________________________________________________________________________

                                      TABLE 24                                    __________________________________________________________________________           Symbol of                                                                          Hard coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                      Type   Substrate                                                                          First Layer                                                                         Second Layer                                                                         Third Layer                                                                          Fourth Layer                                                                         Fifth Layer                            __________________________________________________________________________    Method of                                                                          61                                                                              A    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (a)(4)                                                              TiN (0.3)                              Present                                                                            62                                                                              A    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (b)(7)                                                              TiN (0.3)                              Invention                                                                          63                                                                              A    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (c)(10)                                                             TiN (0.3)                                   64                                                                              B    TiC (6)                                                                             TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (c)(3)                                                              TiN (0.3)                                                                            --                                          65                                                                              B    TiC (6)                                                                             TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (c)(5)                                                              TiN (0.3)                                                                            --                                          66                                                                              B    TiC (6)                                                                             TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (d)(7)                                                              TiN (0.3)                                                                            --                                          67                                                                              C    p-TiCN (6)                                                                          TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (e)(3)                                                              TiN (0.3)                                                                            --                                          68                                                                              C    p-TiCN (6)                                                                          TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (f)(5)                                                              TiN (0.3)                                                                            --                                          69                                                                              C    p-TiCN (6)                                                                          TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (g)(7)                                                              TiN (0.3)                                                                            --                                          70                                                                              D    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (h)(10)                                                             TiN (0.3)                                   71                                                                              D    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (i)(12)                                                             TiN (0.3)                                   72                                                                              D    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (j)(15)                                                             TiN (0.3)                                   73                                                                              E    TiC (2)                                                                             TiCNO (0.3)                                                                          Al.sub.2 O.sub.3 (k)(1.5)                                                            TiN (0.3)                                                                            --                                          74                                                                              E    p-TiCN (2)                                                                          TiNO (0.3)                                                                           Al.sub.2 O.sub.3 (l)(1.5)                                                            TiN (0.3)                                                                            --                                          75                                                                              E    TiN (2)                                                                             TiO.sub.2 (0.2)                                                                      Al.sub.2 O.sub.3 (m)(2)                                                              --     --                                     __________________________________________________________________________

                                      TABLE 25                                    __________________________________________________________________________             Symbol of                                                                          Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                    Type     Substrate                                                                          First Layer                                                                         Second Layer                                                                         Third Layer                                                                          Fourth Layer                                                                         Fifth Layer                          __________________________________________________________________________    Conventional                                                                         41                                                                              A    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(4)                                                              TiN (0.3)                            Method 42                                                                              A    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(7)                                                              TiN (0.3)                                   43                                                                              B    TiC (6)                                                                             TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(3)                                                              TiN (0.3)                                                                            --                                          44                                                                              B    TiC (6)                                                                             TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(5)                                                              TiN (0.3)                                                                            --                                          45                                                                              C    p-TiCN (6)                                                                          TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(3)                                                              TiN (0.3)                                                                            --                                          46                                                                              C    p-TiCN (6)                                                                          TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(5)                                                              TiN (0.3)                                                                            --                                          47                                                                              D    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(10)                                                             TiN (0.3)                                   48                                                                              D    TiN (0.3)                                                                           1-TiCN (5)                                                                           TiCO (0.3)                                                                           Al.sub.2 O.sub.3 (n)(12)                                                             TiN (0.3)                                   49                                                                              E    TiC (2)                                                                             TiCNO (0.3)                                                                          Al.sub.2 O.sub.3 (n)(1.5)                                                            TiN (0.3)                                                                            --                                          50                                                                              E    p-TiCN (2)                                                                          TiNO (0.3)                                                                           Al.sub.2 O.sub.3 (1.5)                                                               TiN (0.3)                                                                            --                                   __________________________________________________________________________

                  TABLE 26                                                        ______________________________________                                                 Al.sub.2 O.sub.3 Layer (Layer Thick-                                          ness of Each Portion: μm)                                                    Flank   Cutting  Rake  Wear of Flank Face                          Type       Face    Edge     Face  (mm)                                        ______________________________________                                        Hard-   61     4.1     4.7    3.7   0.25                                      Material-                                                                             62     7.2     8.0    6.5   0.25                                      Coated  63     10.1    11.2   9.4   0.29                                      Cemented                                                                              64     3.0     3.4    2.8   0.28                                      Carbide 65     4.8     5.7    4.6   0.27                                      Cutting Tool                                                                          66     6.9     8.2    6.5   0.32                                      of Present                                                                            67     2.9     3.3    2.8   0.30                                      Invention                                                                             68     5.0     5.7    4.4   0.31                                              69     7.0     8.1    6.1   0.35                                              70     10.2    11.4   9.0   0.22                                              71     12.1    13.6   11.0  0.24                                              72     14.6    17.0   13.2  0.25                                              73     1.5     1.7    1.4   0.20                                              74     1.4     1.7    1.4   0.22                                              75     2.0     2.3    1.8   0.28                                      ______________________________________                                    

                                      TABLE 27                                    __________________________________________________________________________               Al.sub.2 O.sub.3 Layer (Layer Thickness of                                    Each Portion: μm)                                                                Cutting  Wear of Flank Face                                  Type       Flank Face                                                                          Edge                                                                              Rake Face                                                                          (mm)                                                __________________________________________________________________________    Conventional Hard-                                                                     41                                                                              4.2   7.6 2.0  Usable Life Finished in                             Material-Coated           5.0 min.                                            Cement Carbide                                                                         42                                                                              6.8   11.0                                                                              3.1  Usable Life Finished in                             Cutting Tool              5.5 min.                                                     43                                                                              2.9   5.2 1.4  Usable Life Finished in                                                       7.5 min.                                                     44                                                                              5.0   8.9 2.2  Usable Life Finished in                                                       6.0 min.                                                     45                                                                              2.9   4.7 1.6  Usable Life Finished in                                                       4.0 min.                                                     46                                                                              4.9   8.1 2.7  Usable Life Finished in                                                       2.5 min.                                                     47                                                                              9.7   17.1                                                                              4.0  Usable Life Finished in                                                       7.5 min.                                                     48                                                                              11.6  19.7                                                                              4.5  Usable Life Finished in                                                       5.5 min.                                                     49                                                                              1.5   2.4 0.8  Usable Life Finished in                                                       5.0 min.                                                     50                                                                              1.5   2.6 0.8  Usable Life Finished in                                                       6.0 min.                                            __________________________________________________________________________     (Usable life is finished due to chipping.)                               

                                      TABLE 28                                    __________________________________________________________________________    Hard Coating Layer Forming Conditions                                         Hard                       Reaction Conditions                                Coating                                                                            Composition of Reaction Gas (Vol %)                                                                 Pressure                                                                          Temperature                                    Layer                                                                              AlCl.sub.3                                                                       NO NO.sub.2                                                                         N.sub.2 O                                                                        Ar   He   (torr)                                                                            (°C.)                                   __________________________________________________________________________    Al.sub.2 O.sub.3 (a)                                                               0.5                                                                              10 -- -- Remainder                                                                          --   50  1050                                           Al.sub.2 O.sub.3 (b)                                                               2  10 -- -- Remainder                                                                          --   50  1050                                           Al.sub.2 O.sub.3 (c)                                                               5  10 -- -- Remainder                                                                          --   50  1050                                           Al.sub.2 O.sub.3 (d)                                                               7  10 -- -- Remainder                                                                          --   50  1050                                           Al.sub.2 O.sub.3 (e)                                                               10 10 -- -- Remainder                                                                          --   50  1050                                           Al.sub.2 O.sub.3 (f)                                                               1  -- 1  -- --   Remainder                                                                          100 1050                                           Al.sub.2 O.sub.3 (g)                                                               1   5 -- -- --   Remainder                                                                          100 1050                                           Al.sub.2 O.sub.3 (h)                                                               5  -- -- 15 --   Remainder                                                                          50  1050                                           Al.sub.2 O.sub.3 (i)                                                               5  -- -- 30 --   Remainder                                                                          50  1050                                           Al.sub.2 O.sub.3 (j)                                                               AlCl.sub.3 : 4%, CO.sub.2 : 12%, H.sub.2 : Remainder                                                50  1000                                           __________________________________________________________________________

                                      TABLE 29                                    __________________________________________________________________________           Symbol                                                                        of   Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                      Type   Substrate                                                                          First Layer                                                                         Second Layer                                                                         Third Layer                                                                          Fourth Layer                                                                         Fifth Layer                                                                         Sixth Layer                      __________________________________________________________________________    Method                                                                             76                                                                              A    TiN (0.5)                                                                           1-TiCN (8)                                                                           TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (a)(5)                                                              TiN (0.3)                                                                           --                               of   77                                                                              A    p-TiCN (5)                                                                          TiC (3)                                                                              TiO.sub.2 (0.2)                                                                      Al.sub.2 O.sub.3 (b)(5)                                                              TiN (0.3)                                                                           --                               Present                                                                            78                                                                              B    p-TiCN (8)                                                                          TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (c)(7)                                                              TiN (0.3)                                                                            --    --                               Invention                                                                          79                                                                              B    TiN (0.5)                                                                           1-TiCN (5)                                                                           TiC (3)                                                                              TiCO (0.2)                                                                           Al.sub.2 O.sub.3                                                                    TiN (0.3)                             80                                                                              C    p-TiCN (5)                                                                          TiC (3)                                                                              TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (d)(5)                                                              TiN (0.3)                                                                           --                                    81                                                                              C    TiC (8)                                                                             Al.sub.2 O.sub.3 (e)(5)                                                              TiN (0.2)                                                                            --     --    --                                    82                                                                              D    TiN (0.5)                                                                           1-TiCN (6)                                                                           TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (f)(8)                                                              TiN (0.3)                                                                           --                                    83                                                                              D    TiC (8)                                                                             Al.sub.2 O.sub.3 (g)(8)                                                              --     --     --    --                                    84                                                                              E    p-TiCN (1)                                                                          TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (h)(2)                                                              --     --    --                                    85                                                                              E    TiC (1)                                                                             TiN (2)                                                                              Al.sub.2 O.sub.3 (i)(3)                                                              TiN (0.3)                                                                            --    --                               __________________________________________________________________________

                                      TABLE 30                                    __________________________________________________________________________           Symbol                                                                        of   Hard Coating Layer (Target Layer Thickness shown in                           Parenthesis)                                                      Type   Substrate                                                                          First Layer                                                                         Second Layer                                                                         Third Layer                                                                          Fourth Layer                                                                         Fifth Layer                                                                         Sixth Layer                      __________________________________________________________________________    Conven-                                                                            51                                                                              A    TiN (0.5)                                                                           1-TiCN (8)                                                                           TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (j)(5)                                                              TiN (0.3)                                                                           --                               tions                                                                              52                                                                              A    p-TiCN (5)                                                                          TiC (3)                                                                              TiO.sub.2 (0.2)                                                                      Al.sub.2 O.sub.3 (j)(5)                                                              TiN (0.3)                                                                           --                               1 Method                                                                           53                                                                              B    p-TiCN (8)                                                                          TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (j)(7)                                                              TiN (0.3)                                                                            --    --                                    54                                                                              B    TiN (0.5)                                                                           1-TiCN (5)                                                                           TiC (3)                                                                              TiNO (0.2)                                                                           Al.sub.2 O.sub.3                                                                    TiN (0.3)                             55                                                                              C    p-TiCN (5)                                                                          TiC (3)                                                                              TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (j)(5)                                                              TiN (0.3)                                                                           --                                    56                                                                              C    TiC (8)                                                                             Al.sub.2 O.sub.3 (j)(5)                                                              TiN (0.2)                                                                            --     --    --                                    57                                                                              D    TiN (0.5)                                                                           1-TiCN (6)                                                                           TiCO (0.4)                                                                           Al.sub.2 O.sub.3 (j)(8)                                                              TiN (0.3)                                                                           --                                    58                                                                              D    TiC (8)                                                                             Al.sub.2 O.sub.3 (j)(8)                                                              --     --     --    --                                    59                                                                              E    p-TiCN (1)                                                                          TiCNO (0.2)                                                                          Al.sub.2 O.sub.3 (j)(2)                                                              --     --    --                                    60                                                                              E    TiC (1)                                                                             TiN (2)                                                                              Al.sub.2 O.sub.3 (j)(3)                                                              TiN (0.3)                                                                            --    --                               __________________________________________________________________________

                  TABLE 31                                                        ______________________________________                                                    Al.sub.2 O.sub.3 Layer (Layer Thick-                                          ness of Each Portion: μm)                                                    Flank   Cutting Rake  Wear of Flank                             Type          Face    Edge    Face  Face (mm)                                 ______________________________________                                        Hard-Material-Coated                                                                      76    5.1     5.7   4.5   0.27                                    Cemented Carbide                                                                          77    5.0     5.5   4.5   0.31                                    Cutting Tool of                                                                           78    7.0     7.7   6.4   0.24                                    Present Invention                                                                         79    6.8     7.5   6.3   0.25                                                80    5.0     5.7   4.4   0.25                                                81    5.1     5.9   4.7   0.29                                                82    8.3     9.5   7.2   0.30                                                83    8.0     9.7   7.2   0.33                                                84    2.0     2.4   1.9   0.22                                                85    3.0     3.4   2.6   0.23                                    ______________________________________                                    

                  TABLE 32                                                        ______________________________________                                                Al.sub.2 O.sub.3 Layer                                                        (Layer Thickness of Each                                                      Portion μm)                                                                  Flank  Cutting Rake  Wear of Flank Face                             Type      Face   Edge    Face  (mm)                                           ______________________________________                                        Conventional                                                                          51    4.9    8.7   2.4   Usable Life Finished in 3.5                  Hard-                            min.                                         Material-                                                                             52    4.9    9.5   2.0   Usable Life Finished in 6.0                  Coated                           min.                                         Cemented                                                                              53    7.0    15.1  3.1   Usable Life Finished in 4.0                  Carbide                          min.                                         Cutting Tool                                                                          54    7.0    13.7  2.4   Usable Life Finished in 6.5                                                   min.                                                 55    5.0    8.1   2.1   Usable Life Finished in 3.0                                                   min.                                                 56    4.9    9.4   2.4   Usable Life Finished in 4.5                                                   min.                                                 57    7.9    17.1  3.4   Usable Life Finished in 7.0                                                   min.                                                 58    8.1    16.6  4.1   Usable Life Finished in 6.0                                                   min.                                                 59    2.1    3.4   1.2   Usable Life Finished in 9.0                                                   min.                                                 60    3.1    5.1   1.4   Usable Life Finished in 8.5                                                   min.                                         ______________________________________                                         (Usable life is finished due to chipping.)                               

It is apparent from the above results that the coated cutting tools madeby the method of the present invention, in which the aluminum oxidelayer constituting the hard coating layers is formed using the inert gastype reaction gas, have only very small amounts of local layer thicknessdispersion in the aluminum oxide layer among the hard coating layersconstituting the tools, even if the layer is relatively thick and thelayer thicknesses of the flank face and the rake face of a cuttingportion and the cutting edge where the flank face intersects the rakeface are made uniform, whereas the conventional coated cutting toolsmade by the conventional method using a reaction gas in hydrogen for theformation of the Al₂ O₃ layer have a great amount of dispersion of thelayer thicknesses in a flank face, a rake face, and a cutting edge. Thusthe present coated cutting tools exhibited excellent chipping resistancein the intermittent cutting of steel and cast iron as compared with thatof the conventional coated cutting tools.

As described above, according to the method of the present invention,coated cutting tools in which the aluminum oxide layer constituting thehard coating layer has an increased thickness, give a very small amountof local dispersion in the layer thickness. Consequently, the abovealuminum oxide layer of the present invention coated cutting tools hasthe same characteristics as those of the Al₂ O₃ layer. Additionally, thepresent tools exhibit excellent chipping resistance not only incontinuous cutting but also in intermittent cutting of metals, such assteel and cast iron, and achieve an excellent cutting performance overextended periods of time. Therefore, the present invention provides auseful industrial advantage by contributing to automatic cuttingoperation and labor cost saving in factories.

This application is based on Japanese Patent Applications 08-002292(filed Jan. 10, 1996); 08-068114 (filed Mar. 25, 1996); 08-091025 (filedApr. 12, 1996); 08-092423 (filed Apr. 15, 1996); 08-093966 (filed Apr.16, 1996); 08-304335 (filed Nov. 15, 1996); and 08-304336 (filed Nov.15, 1996), all filed with the Japanese Patent Office, the entirecontents of each of which are hereby incorporated by reference.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A method for preparing a coated cutting toolcomprising:coating a surface of a substrate with a coating layercomprising an aluminum oxide wherein the aluminum oxide layer is formedfrom a reaction gas comprising aluminum trichloride and nitrogen oxidesselected from the group consisting of NO, NO₂ and N₂ O, and mixturesthereof in an inert gas as carrier gas wherein the aluminum oxide layercontains components other than aluminum and oxygen from the reaction gasin a total amount of 15% or less.
 2. The method according to claim 1,wherein the reaction gas comprises, by volume:0.5-10% of aluminumtrichloride: 1-30% of said nitrogen oxides; 0-1% of titaniumtetrachloride; 0-20% of hydrogen; and 0-15% of N₂.
 3. The methodaccording to claim 2, wherein said reaction gas comprises titaniumtetrachloride in an amount of 0.01-1 vol %.
 4. The method according toclaim 3, wherein said reaction gas comprises titanium tetrachloride inan amount of 0.1-0.5 vol %.
 5. The method according to claim 2, whereinsaid reaction gas comprises N₂ in an amount of 1-15 vol. %.
 6. Themethod according to claim 2, wherein said reaction gas compriseshydrogen in an amount of 0.5-20 vol %.
 7. The method according to claim6, wherein said reaction gas further comprises hydrogen in an amount of1-10 vol%.
 8. The method according to claim 2, wherein the amount ofaluminum trichloride is 2-7 vol. % and the amount of said nitrogenoxides is 5-20 vol %.
 9. The method according to claim 1, wherein thecoating step is performed at a temperature of 850°-1150° C.
 10. Themethod according to claim 9, wherein the coating step is performed at apressure of 20-200 torr.
 11. The method according to claim 10, whereinthe pressure is 40-100 torr.
 12. The method according to claim 9,wherein the temperature is 900°-1100° C.
 13. The method according toclaim 1, wherein the inert gas in said reaction gas is Ar gas.
 14. Themethod according to claim 1, which additionally comprises depositing oneor more layers in addition to the aluminum oxide layer, and wherein allthe layers together have an average thickness of 3-20 microns.
 15. Themethod according to claim 1, wherein the substrate is a cementedcarbide.
 16. The method according to claim 1, wherein the aluminum oxidelayer contains components other than aluminum and oxygen from thereaction gas in a total amount of 10% or less.
 17. The method accordingto claim 1, wherein the nitrogen oxides component is NO.